1. Field of the Invention
The present invention relates to a lens frame structure for optical axis adjustment.
2. Description of the Related Art
In recent years small and high-resolution lens systems have been required for lens systems in digital cameras or the like. As a consequence, it is often the case that the focusing sensitivity (eccentricity sensitivity) of a lens group in a lens system becomes very large. The lens group can be a single lens or a plurality of lenses. For instance, a tolerance of eccentricity of a lens group having a high focusing sensitivity is required within a range of a few micrometers. In order to minimize the eccentricity of a lens group, conventionally the precision of the fit between the lens group and a lens frame thereof or the precision of the fit between a lens frame that supports the lens group and another lens frame have been increased. However, it is very difficult to minimize the eccentricity of a lens group to within a few micrometers simply by increasing such precisions.
The present invention has been devised in view of the problems noted above. The present invention provides a lens frame structure which makes it possible to carry out a centering operation on a lens group without relying on the aforementioned precisions of the fit between the lens group and a lens frame thereof or the precision of the fit between a lens frame that supports the lens group and another lens frame.
For example, a lens frame structure for optical axis adjustment is provided, including a first frame having a central opening and a first reference surface normal to an optical axis; a second frame supporting a lens group to be aligned with the central opening, the second frame having a radial flange which has a second reference surface normal to the optical axis and contacting the first reference surface so that the second frame is movable in a direction normal to the optical axis; and a plurality of cutout portions formed on the radial flange, wherein an adhesive is inserted into each of the plurality of cutout portions to bond the second frame to the first frame.
It is desirable for the second frame to be provided with a cylindrical portion to be inserted to the central opening of the first frame with a radial clearance so that the second frame is movable in a direction normal to the optical axis.
The radial flange can be divided into a plurality of radial lugs on which the plurality of cutout portions are respectively formed.
Each of the plurality of cutout portions can be recessed radially inwards from an outer edge of a corresponding one of the plurality of radial lugs so as to be substantially rectangular in cross section.
Each of the plurality of cutout portions can be recessed radially inwards from an outer edge of corresponding one of the plurality of radial lugs so as to be substantially semicircular in cross section.
A plurality of recesses can be formed on the first reference surface to correspond to the plurality of cutout portions, respectively, the adhesive permeating into the plurality of recesses from the plurality of cutout portions, respectively, when the adhesive is inserted into the plurality of cutout portions.
It is desirable for the plurality of recesses to be larger than the plurality of cutout portions in a direction perpendicular to the optical axis.
The lens frame structure can further include a relative positioning device for positioning the second frame relative to the first frame at a predetermined rotational angle.
The adhesive can be a UV curable adhesive.
The lens frame structure can include a relative positioning device for positioning the second frame relative to the first frame at a predetermined angle of rotation, wherein the relative positioning device includes a reference recess formed on the first reference surface, and a reference cutout portion formed on the second reference surface. The plurality of cutout portions are respectively aligned with the plurality of recesses in an axial direction of the first member and the second member by aligning the reference cutout portion with the reference recess in the axial direction.
It is desirable for the reference recess to be formed smaller than each of the plurality of recesses to be visually distinguishable from each of the plurality of recesses.
It is desirable for the reference cutout portion to be formed smaller than each the plurality of cutout portions to be visually distinguishable from each the plurality of cutout portions.
The lens element can be a cemented lens including a front lens element and a rear lens element which are cemented to each other, the rear lens element being directly supported by the second frame so that the front lens element is supported by the second frame via the rear lens element.
The first frame can be guided in an optical axis direction.
The lens frame structure can be incorporated in a zoom lens barrel, the first frame being moved in an optical axis direction to perform a zooming operation.
The lens frame structure can be incorporated in a digital camera.
In another embodiment, a lens frame which supports a lens group is provided, including a first ring portion having a central opening and a first reference surface extending in a radial direction of the first ring portion, and a second ring portion supporting at least one lens element of the lens group and having a second reference surface extending in a radial direction of the second ring portion, the second ring portion being fitted into the first ring portion in a state where at least a part of the second ring portion is loosely fitted in the central opening with the second reference surface remaining in contact with the first reference surface. The second ring portion includes at least one radial flange on which the second reference surface is formed, and a plurality of cutout portions formed on the at least one radial flange, an adhesive being put into each of the plurality of cutout portions to bond the second ring portion to the first ring portion.
The present disclosure relates to subject matter contained in Japanese Patent Application No.2001-203428 (filed on Jul. 4, 2001) which is expressly incorporated herein by reference in its entirety.